One or more cameras are typically provided on a machine to capture an image feed of an area surrounding the machine. The cameras can provide many assistance functions to a driver such as lane keeping, parking aid, detection of obstacles and other objects, vehicle detection, and collision avoidance. Augmented reality may be used to overlay assistance information on the image feed that the driver of the machine is looking at. In order to properly overlay the information, a position and an orientation of the camera must be determined. Determining the position and the orientation is referred to as extrinsic calibration of the camera.
For some applications, an absolute position and orientation of the camera may be required to be referenced to Global Navigation Satellite System (GNSS) coordinates. For other applications, a relative position and orientation of the camera may be required only to be referenced to the ground. It may be difficult to obtain a high accuracy camera calibration for automotive or heavy-duty machines. Further, if the position and the orientation of the camera are not determined with a high enough accuracy, the information overlaid on the image feed may not correlate with reality. Sometimes, the information may be at an offset with the image feed and may seem to be floating around in space. Accordingly, there may be an increased challenge when performing installations, maintenance, or adjustments in the field.
Known solutions include providing large checkered tarps or surveying stakes at a predefined location for calibrating the camera. However, adjusting and calibrating the camera using such a set-up is tedious, time consuming, and may even be labor intensive. Further, the checkered tarps and/or surveying stakes may be difficult to deploy and store.
U.S. Pat. No. 7,089,776 describes a jig for use in certifying accuracy of a vehicle wheel aligner. The jig includes two axles of equal length having stub shafts at the ends of the axles and two adjustable side spacers for releasable connection to the stub shafts. Plates for mounting heads of the aligner system also are attached to the stub shafts. Stands support the corners of the rectangular jig formed by the connected axles and spacers. The aligner system measures parameters of the jig from the attached heads. A diagonal spacer of a predetermined length, may be used in setting the diagonals of the rectangular jig during assembly to be equal. In the example disclosed, the apparatus also includes a distance setting shaft for use in setting lengths of each of the two side spacers to be equal.